


Bitter and Sweet

by NihilismPastry



Series: Requests from Tumblr [2]
Category: Undertale (Video Game)
Genre: Alternate Universe - Underfell, Chubby Reader, Ecto-Penis, Ecto-Tongue (Undertale), F/M, Face Sitting, Female Reader, First Time, Magic dick, body praise, body worship kink
Language: English
Status: Completed
Published: 2016-10-03
Updated: 2016-10-03
Packaged: 2018-08-19 04:22:31
Rating: Explicit
Warnings: Creator Chose Not To Use Archive Warnings
Chapters: 1
Words: 4,124
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/8189779
Author URL: https://archiveofourown.org/users/NihilismPastry/pseuds/NihilismPastry
Summary: Sans surprises his girlfriend by, amazingly enough, not being a jerk.





	

**Author's Note:**

> A gift for life-sans-sin over on Tumblr. Happy kinktober, mama!
> 
> Request: A chubby female reader and Underfell Sans having their first time. Include face sitting and praise kink.

It was snowing. It wasn't even the nice fluffy snow you saw on the cover of holiday cards. Instead it was that wet slushy stuff that got in your boots, clung to your clothes, and made you feel utterly miserable as you marched through the stuff. You'd rather be anywhere but in the middle of the park, but your boss wanted a hotdog, and since you were the mindless worker drone you had to deliver. At least she didn't want a gourmet one this time, that would involve a bus ride across town.

You side stepped a couple pushing a pair of twins in a baby stroller, barely managing to get past them and the most inconvenient trashcan of all time. The woman shook her head and muttered something to her partner, her eyes glancing back to you. A dark blush covered your face, and it took everything you had to keep your head held high and to keep waking. She's just a stranger, a judgmental jackass that you're never gonna see again. You repeated your boyfriends crude advice as you trudged to a beat up food stand under an old pine tree. A lump of black and red was laying against the metal, making a tired smile curl on your lips.

You carefully knocked on the cold metal. "Hey, Edgelord~."

A deep grunt rumbled from the lump, before a bright red pupil looked up at you. "well if it ain't, sweet cheeks." He sat up from his slouched position, his hood falling back to reveal his skull. "what's a girl like you doin' in a hole like this?"

"My boss wants food." You pulled your wallet out of your purse and took out a crumpled twenty. "Two hot dogs with all the trimmings, please." You watched him spear a hot dog and put it in a crusty bun. "And don't add anything weird to it this time, my boss nearly killed me when he found those pill bugs in the ketchup."

"ya told me to give him the special."

"Sans..."

He grabbed a ketchup bottle and squeezed the red liquid all over the hot dog and it's toppings. "fine, but ya gotta give me somethin' in return."

"What would that be?"

He just shrugged. "dunno, i'll think 'bout it and tell ya when i get home." 

He handed you the hot dogs and settled back down on the table top. You snatched a napkin off the pile by Sans's elbow and covered up the food. "Are you inviting me to stay the night?"

He waved you off with his phalanges. "don't get excited, i just wanna get payed."

"Right~." You leaned over the cart and kissed the top of his skull, earning a half hearted glare. "See ya tonight, Edgelord."

* * *

Even though you had joked with Sans about his 'payment', you were still a bit worried about what it would be. Sans had a love for payback, and could forget everything under the sun _except_ for that. The mental image of you cleaning his house in lacy lingerie followed you all through out work. More than once your fellow secretary Laura had to drag you back to earth before your boss noticed your mental absence.

As you climbed the stairs to your boyfriend's trailer, your fingers repeatedly combed through your hair as a soothing gesture. Sans was an asshole, but he wouldn't do something you didn't want to do. You took a calming breath and knocked on the door, and quickly shoved your hands back in your pockets. It was freezing out, more snow was being dumped from the sky, and it was already getting dark. Snowflakes tangled in your hair and clung to your clothes. You sighed and kicked at the door, half hoping Papyrus wouldn't notice the black smudge mark on his paint job. 

"Come on Sans." The skeleton was usually late to everything, but you didn't think he'd be late from work. The guy practically lived for time off. 

Slowly the sun began to sink below the horizon. The shadows began to twist around the trees of the property, and the sky became a fascinating shade of dark oranges and purples. But with the beauty came the severe drop in temperature. Even with your thick coat and scarf, you could still feel the cold bite through the fabric. Your body trembled as you leaned against the door, and more than once you had to shake snowflakes out of your hair. You'd try calling him a few times, but of course it went straight to voicemail, the bastard never kept his phone charged. 

You sighed and shut your eyes. Why were you even waiting for him? He would never do the same thing for you. He hated being inconvenienced, and made it clear you would never get special treatment just because you were dating. You were just someone that entertained him, not his lover, not anyone he actually cared about. He's done the same thing so many times, setting you up to fail. Why did you think this time would be any different. You could feel your eyes stinging, and you bit your lip. You weren't gonna cry, not over this asshole. You pushed yourself off the wall and spun on your heel. You were gonna keep at least a shred of your dignity. 

As you went down the wooden steps, you slipped on the slushy snow, and fell face first into the snow. You hissed and tried to scramble up, but your hands were quickly going numb, and slipped from up under you every time you tried to push yourself up. As you sunk your nails into the grey slush, you heard a whirring pop and the smell of a burning fire permeated the area. "the hell are you doin' sweet cheeks?"

You stared at the red shoes that had entered your vision, snow slipping off your face and falling to the ground in watery chunks. You couldn't look at him, all of your earlier anger melted away with the devil himself standing before you. "I..."

A gusty sigh left him and you felt magic crackle around you. Unbidden you felt your body haul itself up into a standing position. More snow slid off your clothes and fell to the ground, but you didn't dare look up at him. "don't tell me you're all weepy cause i'm late. boss needed me-"

"But what about me?"

"sweet-"

"Don't ' sweet cheeks' me!" You looked up at him now, fingers clenched and voice louder than it'd been in a year. "You always manage to let me down, Sans. You drag me along because you know I'll go along with whatever you come up with. You don't love me at all, I'm just a toy!"

Puffs of steam escaped your mouth as you breathed heavily. You felt tired now, all you wanted to do was to home and cry. It didn't help that Sans seemed completely bored by your rant, his pupils staring at you with a blank expression. "you done?"

You roughly wiped at your eyes with a numb hand. "Y-yeah."

"good."

You squealed when he grabbed you around the waist and hauled you onto his shoulder. "Sans, let go you asshole!"

"the hell would i do that?" He marched up the steps and opened the door. It wasn't even locked, all he did was twist the knob and walk into the clean house. "i told you that you could stay over, right?"

"But-"

"yeah, ain't gonna make you walk back home in the snow, sweet cheeks." He kicked open a door, and dumped you on a toilet. "get in the shower, i'll get you some clothes."

He shut the door behind him, leaving you alone. Well that was incredibly strange. Sans didn't go out of his way to touch you, usually he used magic for that sort of thing. You sighed and hauled yourself off the toilet and went over to the mirror above the small sink. Your face was smudged with dirt, and your hair looked limp. Around your eyes were puffy, and you looked much too pale.

If Sans was doing this out of anything, it would be pity. 

You unzipped your coat and put it on the narrow counter. Next came your turtle neck, and the camisole under it. You struggled with your bra for a moment, before that was put away too. You pursed your lips as you stared at your reflection. Too large, pimples, and stretch marks over your tummy and legs. Of course Sans only saw you as a toy. You'd been turned down before due to your looks.

"Sorry, but you're just too...much."

"You still have pimples, what are you fifteen?"

"You're kinda plain, ya know?"

You bit your lip as your fingers curled onto the counter top's ledge. You weren't pretty, so none of the humans you tried to date gave you the time of day. Sans probably only agreed since you were human and that made you 'exotic'. But you weren't pretty, by now even the ever aloof skeleton would have had to realize that. And now that he did he didn't want to waste time on you...

The door slammed open, and you barely had enough time to pull the camisole back on before Sans shuffled in, a red t-shirt in hand. "here, my stuff should fit you-"

"I wanna break up."

You dared to look over at the skeleton. His brow bones were furrowed and his eyes roamed over your face. After a moment he snorted and tossed the shirt onto the sink. "you don't mean it."

"Yeah, I do." You waited for Sans to laugh at you, yell, anything, but he didn't. "You don't make time for me, you break your promises all the time. Why do you even keep me around? I know I'm not pretty like those other humans, and I'm not something you can show off, but..." Huh, of course you couldn't finish. Even though Sans was the biggest jerk in the world, you could still feel your throat constricting and eyes stinging. "I don't want to feel like trash anymore."

"i told you from the beginning, i gotta lot on my plate." He took a step forward. "and i said i ain't gonna treat you special just because we're dating." 

And here it is, the part where he kicked you to the side. Told you that he could find another human, once that he could be proud to show off to his monster friends. Then you could go back to being alone. 

Alone and worthless.

"but where in the fuck did you get human aesthetics outta this?" Your eyes widened when he grabbed your wrist, his bone fingers dug into your skin. "i already get shit from monsters and humans for datin' you, what makes you think I wanted you just for paradin' around like some new magic ability?" His grip tightened. "and if ya doubt me, then we've gotta bigger problem."

"But-"

"yeah, I like your ass." He said. "it's soft as fuck, and feels good on my bones. dunno why you're always sayin' it's too big." His free arm wrapped around your waist to squeeze your ass. You gasped and tried to move away, but that only pushed you closer to him. "fuck, you don't even realize what a luxury you've got, huh? monsters don't have skin like this, it ain't ever soft. closest soft thing you're gonna get is fur and hair."

You flushed at the compliment, but shook your head. "Sans, you basically complimented me for being human, everyone has soft skin-"

"not like yours." The hand on your wrist trailed up your arm to your love handles. You tried to push him away, but he kept you still. "you're soft all over, not all humans are like that." 

"It's called fat, it's from not dieting and-"

"is it?" He squeezed the lump of flesh in his fingers. You yelped, but didn't push him away. "you walk everywhere and eat mostly monster food, ain't nothin' healthier than that. you're gorgeous, sweet cheeks."

"..."

He leaned down and pressed his teeth to your forehead. You opened your mouth, but nothing would come out. Sans had never shown you this much affection before. You'd been over the moon when he held your hand after a month of dating, and it was a blessing when you were upgraded from 'Idiot' to ' Sweet Cheeks'. If you wanted a kiss you had to initiate it, if you wanted a hug you had to go to him. And it could never be in public, he would become irritated and stiff if it was.

So for him to basically run his comfort zone over with a tank was...

You raised your arms and wrapped them around his neck. You lifted your head from his teeth, and replaced it with your lips. His mouth was still warmed by your body heat, and there was the tang of his magic. It was like fire embers and fall, smoky but just so comfortable that you didn't mind. You pulled away first, your blush taking up your entire face by now. "Thanks Sans, you can be really sweet when you wanna."

He stared down at you, a faint red hue dusted along his cheek bones. The arm around your waist constricted and his other had reached out to brush your cheek. "yeah?"

His face inched closer to yours, you could practically feel the magic wafting from his maw. "Yeah."

He pressed his teeth against your mouth. You let your lips mold to his teeth and enjoyed the taste of magic and mustard. A weird combination that just managed to work. As you kissed you could feel a gentle current of magic ignite along his teeth, before there was a full snap, and something warm and tingly was slipping into your mouth. You gasped and leaned back, eyes wide as you stared at him, more appropriately his mouth. For once it was open, and in between the jagged fangs was a bright red appendage. 

"You have a tongue?"

It twisted up and flicked his top row of teeth. "nah, this is just magic."

You leaned forward until the appendage was just a breath from your lips. You could feel the magic radiating from it, and could see it ripple with every movement. You opened your mouth and circled your lips over it, before sliding up the appendage and fitting your mouth over Sans's teeth again. A growl rumbled in the monster's chest, and the tongue flicked around your mouth. When it found your own tongue, it coiled around it, and sent a gentle pulse of magic. 

You moaned and pressed yourself closer to the skeleton, forcing him to take a step backwards and into the hall. He disconnected from you and shut his mouth again. "you've got no idea what you do to me, sweetheart."

"...Will you show me?"

His pupils flickered. "seriously? do you even hear yourself right now?"

Did...Did he not want this? Wait, he was a skeleton, of course he can't exactly show you, not the traditional way. But that was fine, you were willing to experiment. "Sans, I didn't-"

"you mean it?" He said, his voice was low, just gravel and bass. "you want what i can give you?"

 You bit your lip, but nodded none the less. As if someone pulled a switch, Sans grabbed you and tossed you over his shoulders like a bag of potatoes. You squealed, but it came out more like a laugh.

"Sans!"

* * *

  You found yourself on your back, springs digging into your spine, and bony fingers sinking into your hips. Your lips were connected to his teeth, and his tongue was exploring your mouth. There was an urgency to Sans's movements. Every time you would pull away, he would bring you right back with a low growl that made your insides flutter.

A hand reached up and began to tug at your camisole, exposing your stomach to the cold air of the room. You gripped his jacket harder, a protest on your lips, but he shook his head. "already told you that you're gorgeous sweet heart, i don't care about human ideals. let me see your sexy body."

You let go of his jacket and arched your back, making it easier for the white camisole to slip over your body and get flung to the cluttered floor. With your upper body completely exposed to the skeleton, your face burned a dark red and you turned your head to the side, but cold fingers grabbed your chin and tilted your head back. Red pupils stared down at you, their ever intense and mocking look gone. Their was something else their, it was softer than lust, but harder than adoration. 

You raised a hand and pressed it against the hand on your face. Slowly gripping it, you let the phalanges trail down your neck and sternum until they reached your breasts. A faint red dusted Sans's face, but he didn't falter as he squeezed the soft flesh. You sighed and relaxed into the bed again, enjoying his rough fingers work circles into the flesh. Your nipples were soon erect, and it didn't take long for Sans to realize that they were especially sensitive. 

He hunched down closer to your body and lashed his tongue around the left nipple, while squeezing the other between his fingers. Sweet moans escaped your lips, and your legs slid upwards, encircling around his thin hip bones. "that's it sweetheart, sing for me."

It amazed you really, seeing someone who was so strong and dominate, be so gentle with you. Whenever his teeth grazed your skin, he would quickly lick away the pain and mumble apologizes. He if pinched too hard, his fingers would slacken and he found a new area until the stinging stopped. You were no virgin, but it was the first time you felt...

Loved.

Cherished.

 ** _Wanted_**.

He flicked open the button to your jeans and sat up. "we're gonna try somethin' real quick. you alright with that?"

 You barely managed to croak out your approval before he hand flipped you both over. You latched onto his ribs for support and had to blink away the spinning room. Once you saw only one Sans, your face heated up. "Sans I shouldn't be on top, I'm too-"

He grabbed your ass and ground his pelvis into your clothed core. "baby, i'm strong enough to handle you. relax alright, let me show you what you do to me." You nodded hesitantly, and he latched onto your consent. "go ahead and take off your pants and stuff."

You swung a leg off of him and curled your fingers into your belt loops. You glanced back to your boyfriend, and bit your lip. This was really happening, after this things would be different. Well, for you, maybe not for him. You'd become far more attached to him, and his let downs would stab deeper. Could you handle that? 

_Yes._

He wasn't ashamed of you. He loved you. Doing this was his way of showing you that love. You pulled your thick jeans down your legs and kicked them off. Next went your underwear and socks, all thrown to the cluttered floor. You moved to remount his pelvis, but he grabbed your wrist. "up here baby, get on my face."

"Huh?"

He grinned, it was one he usually flashed his brother when he was trying to come across innocent. "come on, let me see you close up, baby."

You crawled over him, careful not to lean your full weight on any of his bones. "Fine, but don't come crying to me when I crush your skull." You set your pussy over his mouth, and pressed your shaking hands against the cream wall. You'd never been in this position before. Usually it was missionary, and occasionally doggy style, but you were never on top. 

You gasped when you felt something thick and warm flutter around your outer lips. Your toes curled and unfurled with each flutter of his tongue along your pussy. It'd been awhile since someone ate you out, as the tongue wedged between your lips, you were almost sure you were going to orgasm without even trying. You could feel his magic pulse through his appendage, as it began exploring your clint, you could feel the magic soak into it in waves. 

"taste so good, baby." His voice was muffled by your body, something about that fact sent a shot of pure fire down to your core. "sittin' all nice and pretty for me. so good, sweetheart."

His tongue somehow circled your clit and you gasped. It only became louder when you felt bones pry apart your lips, and circle your tight hole. Each rotation he would sink a centimeter of his phalange into your body, but would remove it before it could go deep enough to actually do anything to you. You probably would have complained, but the work he was doing on your clit was perfect. Harsh circles with magic pulse around it, occasionally you could feel a phalange give a hard pinch. 

"Sans~!"

"close, huh? You ready to cum, sweetheart?" He sunk a finger into your cunt and began to mercilessly pound into you. Your back arched and a broken whine escaped your lips. "let me hear you, sweetheart. you sound so good."

A flick of his tongue and a well aimed thrust and it was over. Your head fell forward and his name escaped your lips as an orgasm washed through you. Sans lazily pumped his finger through your entire orgasm, effectively drawing it out. "good girl, you did so well."

You let out a small laugh. "T-thanks, Sans."

"don't go thankin' me yet," He said, gripping your hips and slowly pulling you off his face to reveal a single burning pupil. "we're just gettin' started."

"Huh?" You heard a zipper go down, before there was a flash of red in your peripheral vision. You turned your head and gasped. Standing proud from Sans's fly was a cock. A bright red cock that was clearly magic, a decent length, and a girth that made you drool. "That's..."

He chuckled and let you inspect it. "take it you approve?"

You gently touched the head, earning a grunt from Sans. It was warm and you could feel the magic ripple through it. "Yeah."

"climb on then, baby." You didn't need the extra prompting. If he could take you on his skull, then his hips would be fine. 

You straddled his hips and let his cock caress your stomach. You looked back up to him, but he just gestured to his dick. Taking that as an ok, you lifted yourself up and gripped his base. The first inch felt like heaven. The sting of your walls, his growl of pleasure, and the pulse of magic nearly floored you. Slowly you made your way down his dick, stopping whenever it became too much, until you were eventually seated in his lap. His phalanges dug into your hips and he stared at you with a predatory expression. "ready?"

You straightened your back and pulled yourself up a few inches, before sliding back down. He huffed out a laugh and began thrusting into you. He set a hard pace, his dick hitting deep inside of you and grinding against your walls. Even though you were on top, it felt like he was controlling everything. Whenever you cried about because he hit the perfect spot, he was quick to find it again. When your hands went up to play with your breasts, he would reach up and swat your hands away, and fondle them himself. 

It felt so good to be doted on like this, to be pleased entirely by another person. You stared down at that red hued skull, a soft smile curling on your lips as you leaned down and kissed him. He opened up his mouth and let his tongue snake into your mouth. You couldn't taste yourself, the fluids must have disappeared when his tongue did. His hands let go of your breasts and trailed down to your hips again. You parted from the kiss, and pressed your hands against his cheek bones. "Sans, how do you want me to pleasure you?"

He slowed his thrusts and shook his head. "it's about you, baby." With a little help from his magic he flipped you both over, and leered down at you, picking up his pace. "i'm gonna make you cum. you're gonna cum, and cum, and cum til you can't anymore. that's what you do to me, sweetheart." He leaned down, his voice a low rumble.

" _ **you drive me insane**_." 

**Author's Note:**

> Believe it or not, this is my very first time writing something 100% vanilla. Hopefully it isn't complete shit. 
> 
> You know what isn't shit? My tumblr! http://nihilismpastry.tumblr.com


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